This application claims priority of Japanese Patent Application No. 2000-126587, filed Apr. 26, 2000, and Japanese Patent Application No. 2000-154589, filed May 25, 2000.
1. Field of the Invention
The present invention relates to a heating apparatus that is housed within a reaction chamber, which is used for heating an object to be heated, such as a wafer or the like, and is able to achieve marked improvements with respect to both its heating efficiency and product life.
2. Relevant Art
Conventionally, as an example of a heating apparatus that is housed within a reaction chamber and used for heating an object to be heated such as a wafer or the like, a heating apparatus is known, which comprises a heating block that is divided into two parts. Among these two divisions of the aforementioned heating block, the heating block onto which the object to be heated is placed (hereinafter referred to as xe2x80x9cloading platexe2x80x9d) comprises a material that has a comparatively high coefficient of thermal conductivity, such as stainless steel, iron or the like. The other heating block (hereinafter referred to as xe2x80x9csupport platexe2x80x9d) comprises a material that displays a lower coefficient of thermal conductivity than the material comprising said loading plate, such as ceramics, chinaware, building stone, or the like. In addition, the aforementioned conventional heating apparatus comprises a structure in which a heating element is sandwiched in between the aforementioned loading plate and support plate. In this manner, this heating apparatus is able to heat the aforementioned loading plate by means of concentrating the heat generated by the heating element to the loading plate, and consequently displays a high heating efficiency.
In addition, as another example of a conventional heating apparatus, a heating apparatus is known which comprises a structure in which a single layer or multiple layers of a heat insulating material are provided in between a surface heating member, formed by means of burying a heating element within a ceramics sintered body possessing a superior thermal conductivity, corrosion resistance, and plasma resistance; and a support member, which supports this heating member and connects to a reaction chamber, wherein this heat insulating material limits the heat conducted from the aforementioned surface heating member to said support member.
FIG. 5 is a schematic outline showing the cross-sectional structure of an example of a conventional heating apparatus. The structure of this heating apparatus 1000 will be described in the following. This heating apparatus 1000 comprises a surface heating member 103, a heating element 108, an electrode plate 104, a heat insulating material 113, and a support member 102.
As shown in FIG. 5, heating apparatus 1000 internally comprises a structure in which a single layer of a heat insulating material 113 is sandwiched in between a surface heating member 103, comprising a heating element 108 having a predetermined shape (e.g., spiral-shaped) and a disk-shaped electrode plate 104 for generating plasma, and a support member 102. In this heating apparatus 1000, both the heat insulating material 113 and surface heating member 103, as well as the heat insulating material 113 and support member 102 are joined in an airtight manner.
The surface heating member 103 is equipped with a first ceramics sintered body 103a for holding heating element 108, a second ceramics sintered body 103b for holding electrode plate 104, and a third ceramics sintered body 103c onto which the object to be heated is placed. The first ceramics sintered body 103a and second ceramics sintered body 103b, as well as, the second ceramics sintered body 103b and third ceramics sintered body 103c are respectively joined in an airtight manner by means of bonding layers 110 and 107, each respectively comprising a heat-resistant bonding agent.
In addition, as seen in FIG. 5, heating element 108 is loaded within concave member 112, which is provided along the shape of heating element 108, on the upper surface of the first ceramics sintered body 103a in the figure; and electrode plate 104 is loaded within concave member 111, which is provided on the upper surface of the second ceramics sintered body 103b in the figure.
One pair of heater feeding electrodes 109 is connected to the aforementioned heating element 108, and a high-frequency/direct current voltage application electrode 105 is connected to electrode plate 104. In addition, a thermocouple 106, one terminal of which is inserted into surface heating member 103, is provided in heating apparatus 1000 for measuring the temperature within surface heating member 103.
However, in this type of heating apparatus wherein the loading plate comprises a material that has a comparatively high coefficient of thermal conductivity, such as stainless steel, iron or the like, while the support plate comprises a material that displays a lower coefficient of thermal conductivity than that of the material comprising said loading plate, such as ceramics, chinaware, building stone, or the like, due to the inferior plasma resistance of the stainless steel, iron, etc. comprising the loading plate, there exist problems with respect to the short product life of the heating apparatus.
In addition, in the aforementioned heating apparatus, it is difficult to match the coefficient of thermal expansion of the support plate, which is able to decrease the amount of heat dissipated, and the coefficient of thermal expansion of the loading plate, and thus a difference in these coefficients of thermal expansion inevitably appears. As a result, the durability of the bonding interface between the support plate and the loading plate is insufficient, thereby contributing to the problem of the short product life of this heating apparatus.
In addition, in the construction of the heating apparatus 1000 shown in FIG. 5, problematic restrictions on the structural material of the heat insulating material 113 exist due to the exposure of the side surface of the heat insulating material 113 to the anti-corrosive atmospheric gas, plasma, and the like. As a result, in addition to the restrictions on the structural material of the heat insulating material 113, since it is difficult to approximate the difference in the coefficients of thermal expansion of surface heating member 103 and insulating material 113, or difference in the coefficients of thermal expansion of insulating material 113 and support plate 102, the structure of the aforementioned heating apparatus is extremely complex, leading to a problematic increase in cost.
In order to solve the aforementioned problems, the present invention provides a heating apparatus that displays both a high heating efficiency and a long product life.
Specifically, it is an object of the present invention to provide a heating apparatus comprising a superior plasma resistance, wherein an improvement of the durability of the interface generated by the difference in the coefficients of thermal expansion of the loading plate and support plate is realized while maintaining a high heating efficiency.
In addition, the present invention provides a heating apparatus with a superior heating efficiency, which is free of any restrictions on the structural material of the heat insulating material and is, moreover, easily manufactured at low cost, wherein the product life is further increased.
In order to achieve the aforementioned objects, the present invention utilizes the following construction.
The present invention provides a heating apparatus characterized in comprising: a loading plate onto which an object to be heated is placed; a support plate that is integrated into a single body with said loading plate; a heating element which is sandwiched in between said loading plate and said support plate; and at least one pair of electrodes, one terminal of which is connected to said heating element; wherein, said loading plate and said support plate each respectively comprises a ceramics sintered body, such that the coefficient of thermal conductivity of said ceramics sintered body comprising said loading plate is greater than the coefficient of thermal conductivity of said ceramics sintered body comprising said support plate.
According to the present invention, since the loading plate and support plate each respectively comprise a ceramics sintered body, it is possible to approximate the values of the coefficients of thermal expansion of the loading plate and support plate, which in turn results in an improvement of the interface strength between the aforementioned, thereby allowing for an increase the durability, plasma resistance, and product life thereof.
In addition, the coefficient of thermal conductivity of the loading plate is greater than the coefficient of thermal conductivity of the support plate, and thus the heat generated from the heating element can be concentrated in the loading plate and transferred therefrom. Furthermore, it is possible to effectively prevent heat dissipation to the support plate, onto to which the object to be heated does not rest, while maintaining the coefficient of thermal conductivity of the side onto which the aforementioned object does rest, and thus dramatically improve the heating efficiency of this heating apparatus.
Subsequently, the present invention provides a heating apparatus characterized in comprising: a loading plate onto which an object to be heated is placed; a support plate that is integrated into a single body with said loading plate; a heating element which is sandwiched in between said loading plate and said support plate; and at least one pair of electrodes, one terminal of which is connected to said heating element; wherein, said loading plate and said support plate each respectively comprises a ceramics sintered body; said heating element is loaded within a concave member provided at the bonding surface of either or both of said loading plate and said support plate; and said heating apparatus is further equipped with a heat insulating material arranged at least at the base of said heating element.
According to the present invention, since the heat insulating material is loaded within a concave member provided at the bonding surface of either or both of the base member and plate to be covered, this heat insulating material is not exposed to anti-corrosive atmospheric gas, plasma, and the like, and thus the structural material comprising this heat insulating material is free of restriction, allowing for an easily manufactured, low cost heating apparatus with a further improved product life.
In addition, the heating apparatus of the present invention is equipped with a heat insulating material arranged at least at the base of said heating element (i.e., the side onto which the object to be heated is not placed), and thus it is possible to prevent dissipation of heat from the side onto which the object to be heated does not rest, while also maintaining the thermal conductivity of the side onto which the object to be heated does rest, which in turn results in a superior heating efficiency.
In addition, in the heating apparatus of the present invention, the heat insulating material is preferably selected from among a metal or ceramics such as aluminum nitride, silicon nitride, a siliceous material, alumina and the like. In the case when the heat insulating material is formed from the aforementioned, it is possible to efficiently insulate the heat generated by means of the heating element.
In addition, in the heating apparatus of the present invention, the ceramics sintered body preferably comprises an aluminum nitride sintered body using Y2O3 as an auxiliary agent or an aluminum nitride group sintered body using Y2O3 as an auxiliary agent. By means of employing such a structure, it is possible to reduce the addition amount of the Y2O3, which in turn allows for easy control of the thermal conductivity of the aluminum nitride group sintered body.
In addition, in the heating apparatus of the present invention, the Y2O3 blending amount of said ceramics sintered body of said loading plate is preferably greater than the Y2O3 blending amount of said ceramics sintered body of said support plate.
By constructing the aforementioned loading plate and support plate in this manner, it is possible to reduce the thermal conductivity of the support plate to below that of the loading plate, and also reduce the heat dissipation from the support plate side, onto which the object to be heated does not rest. As a result, it is possible to increase the heating efficiency.
In addition, in the heating apparatus of the present invention, said loading plate and said support plate are preferably bonded together into a single body by means of a vitreous bonding layer. According to this type of structure, it is possible to improve the strength of the bonding surface between the loading plate and support plate, in addition to increasing the degree of air-tightness at the bonding surface of the aforementioned. As a result, by improving the strength of the bonding surface, it is possible to increase the product life of the heating apparatus.
In addition, in the heating apparatus of the present invention, said loading plate comprises a head plate and base plate, which in turn allows for the installation of an electrode plate, sandwiched between said head plate and said base plate, and an electrode, which is connected to said electrode plate. According to this structure, it is possible to apply the aforementioned heating apparatus to various uses by means of varying the usage of the electrode plate.